Demolition shear attachments which mount to the end of a boom or stick of an excavator and which are used for cutting or shearing steel I-beams, channels, pipes, metal plate and other materials are well known. Such shear attachments typically have a main body supporting a fixed lower jaw and a movable upper jaw which pivots about a pivot pin. The upper jaw is moved between an open position and a closed position by extending and retracting a hydraulic cylinder or actuator protected within the main body. Hardened steel blades are attached to one side of the upper and lower jaws (i.e., the “blade-side”). In use, the shear attachment is positioned such that the workpiece to be cut or sheared is positioned between the open jaws. As the jaws close over the workpiece, the adjacent edges of the hardened steel blades on the upper and lower jaws pass in close proximity to each other shearing the workpiece along a shear plane, much like a scissors.
It is recognized that when the upper jaw begins to shear through a workpiece, tremendous lateral forces are exerted on the upper jaw in the direction away from the blade-side of the lower jaw (i.e., toward the “guide-side” of the lower jaw). These lateral forces produce a moment in the direction of the lateral forces about the pivot pin. If the upper jaw is not restrained to resist these lateral forces by providing an opposing reactionary force and counteracting moment, the forward end of the upper jaw will tend to translate laterally away from the blade-side of the lower jaw. Thus, without a reactionary force and counteracting moment to prevent the upper jaw from translating laterally, sever stress can be exerted on the pivot pin potentially bending, shearing or otherwise damaging the pivot pin and the upper jaw.
To restrain the upper jaw from translating laterally by providing a reactionary force and counteracting moment, and to thereby minimize stress on the pivot pin and the upper jaw, lateral stabilizers are employed such as disclosed in U.S. Pat. Nos. 6,061,911 and 7,216,575. These lateral stabilizers have heretofore been positioned in the main body of the shear attachment so as to bear against the blade-side of the upper jaw rearward of the pivot pin and to bear against the guide-side of the upper jaw forward of the pivot pin so as to provide the necessary reaction forces and counteracting moments to prevent the upper jaw from translating laterally during the shearing operation.
While positioning lateral stabilizers in the main body of the shear attachment may serve the intended purpose, positioning a lateral stabilizer on the main body rearward of the pivot pin may not be feasible in certain configurations of the shear attachment. For example, in shear attachments which utilize dual actuators to open and close the upper jaw, there may be insufficient space in which to mount the lateral stabilizer in the main body rearward of the jaw pivot pin without interfering with the second actuator. Accordingly, there is a need for an alternative means of laterally stabilizing the upper jaw of a demolition shear attachment where the lateral stabilizer is not mounted within the main body of the shear attachment.